rubber cycle


May 29, 2022

The rubber cycle was a moment in the economic and social history of Brazil, related to the extraction of latex from the rubber tree and the commercialization of rubber. It had its center in the Amazon region, and provided expansion of colonization, attraction of wealth, cultural, social, architectural transformations, and a great impulse to the growth of Manaus and Belém, until today capitals and largest centers of their respective states, Amazonas and Pará; In addition to many other cities in the region such as: Itacoatiara, Marabá, Rio Branco, Eirunepé, Cruzeiro do Sul and Altamira. In the same period, the Federal Territory of Acre, current State of Acre, was created, whose area was acquired from Bolivia, through the purchase of 2 million pounds sterling, in 1903. The rubber cycle reached its peak between 1879 and 1912, having then experienced a survival between 1942 and 1945, during the Second World War (1939-1945).

General lines

The French naturalist Charles Marie de La Condamine became very interested when he became aware of the sticky and thick sap with which the Amazon Indians, in the 18th century, made objects. This is how he reported his discovery at the French Academy of Sciences in 1774: "The Indians manufacture bottles, boots and hollow balls, which flatten when pressed, but which return to their original shape when freed." The first step was taken there for the advent of the Rubber Cycle. The first factory for rubber products (elastic alloys and suspenders) appeared in France, in Paris, in 1803. However, the material still had some disadvantages: at room temperature, the gum was sticky. As the temperature increased, the gum became even softer and stickier, while the decrease in temperature was accompanied by the hardening and stiffness of the rubber. Central American Indians were the first to discover and make use of the unique properties of natural rubber. However, it was in the Amazon rainforest that the activity of rubber extraction took place, from the rubber tree (Hevea brasiliensis), a tree that belongs to the Euphorbiaceae family, also known as the tree of fortune. A white liquid called latex is extracted from the stem of the rubber tree, whose composition contains, on average, 35% of hydrocarbons, especially 2-methyl-buta-1,3-diene (C5H8), commercially known as isoprene, the rubber monomer. Latex is a virtually neutral substance, with a pH of 7.0 to 7.2. But when exposed to air for a period of 12 to 24 hours, the pH drops to 5.0 and undergoes spontaneous coagulation, forming the polymer that is rubber, represented by (C5H8)n, where n is on the order of 10,000 and has an average molecular mass of 600,000 to 950,000 g/mol. The rubber thus obtained has disadvantages. For example, exposure to air causes it to mix with other materials (miscellaneous debris), which makes it perishable and putrefying, as well as sticky due to the influence of temperature. Through an industrial treatment, impurities are removed from the clot and the resulting rubber is subjected to a process called vulcanization, resulting in the elimination of undesirable properties. It thus becomes imperishable, resistant to solvents and temperature variations, acquiring excellent mechanical properties and losing its sticky character. The rubber tree seed is rich in oil, which can be used as a raw material for the production of resins, varnishes and paints, and, as it is rich in nutrients, it is used in the manufacture of food supplements. Indigenous people still use rubber tree seeds as food.

First rubber cycle: 1879-1912

During the first four and a half centuries of discovery, as no riches of gold or precious minerals were found in the Amazon, the populations of the Brazilian hileia lived practically in isolation, because neither the Portuguese crown